JPH06129579A - Flexible fitting - Google Patents

Abstract

PURPOSE:To provide an anti-corrosive flexible pipe fitting with which the sealing and flexibility can be held for a long time even though it serves being embedded underground by forming it from a resilient substance as a reaction object of a hardening agent and a main material containing liquid rubber which has a specific hardness and compressive elongativeness. CONSTITUTION:Longitudinally stretching, recesses and projections are formed alternately on the internal and external surfaces of a cylindrical body 2 of pipe fitting made of metal. This body 2 of fitting is deformable in the longitudinal direction and is covered with an anti-corrosive covering layer 4, which is in turn covered with an elastic subatance 5A. The substance 5A having a thickness over 5mm even in its thinnest part, consists of a reaction object of a hardening agent and a main material containing liquid rubber, and has a hardness between 5-60 by A-type hardness meter according to JIS-K-6301. Further, the flexible fitting can be compressed to a length below 70 when its original length is 100, and is capable of elongating to 130 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portion in which a joint portion of a pipe for transporting gas, liquid, powder or granules is present, that is, an air-conditioning duct, a gas pipe, water and sewerage, a steam pipe, a chemical plant pipe. The present invention relates to a flexible joint for connecting transportation pipes and the like in a mill for milling and filling agents.

[0002]

2. Description of the Related Art Conventionally, when a joint for connecting pipes has a high rigidity, it is difficult to connect the pipes due to misalignment of the pipes. Further, due to expansion and contraction and vibration of the pipe itself, the vibration was amplified, and the joint part was damaged due to increased stress. On the other hand, the flexible joint made of rubber or plastic has a very excellent sealing effect on the pipe body due to its flexibility at the beginning of service, which is a good result. However, when it is buried, creeping phenomenon and compression set peculiar to polymer materials occur over time due to earth pressure and stress due to expansion and contraction of pipes, gradually losing the sealing function and damaging the joint itself. Accidents began to occur one after another. On the other hand, the flexible joint made of metal has a drawback in that its flexibility is lost due to corrosion and restraint of movement of the uneven portion of the joint due to earth and sand or small stones at the time of burying, and damage to the joint portion due to metal fatigue.

[0003]

The object of the present invention is to provide an excellent sealing effect on the pipe body, even if it is buried underground, the sealing function is not lost for a long period of time, the corrosion resistance is high, and the flexibility is long-term. It is to provide a flexible joint that can be held.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a tubular joint body made of metal, in which concave and convex portions are alternately formed in the longitudinal direction on the inner peripheral surface and the outer peripheral surface of the joint main body. A joint body that is deformable in the longitudinal direction; an anticorrosion coating layer that covers the outer peripheral surface of the joint body; and an elastic body that covers the outer periphery of the anticorrosion coating layer, with the thinnest portion having a thickness of 5 mm or more. However, the flexible joint is composed of a reaction product of a base material containing a liquid rubber and a curing agent, and has an elastic body having a hardness of 5 or more and 60 or less in an A-type hardness meter specified in JIS-K-6301. The original length of the flexible joint can be compressed to 70 or less, and the original length of the flexible joint can be compressed to 130 or more. A flexible joint that is extendable up to.

Further, the present invention is a tubular joint body made of metal, wherein concave portions and convex portions are alternately formed in a longitudinal direction on an inner peripheral surface and an outer peripheral surface of the joint body. Joint body that can be deformed into: an anticorrosion coating layer that covers the outer peripheral surface of the joint body; an elastic body made of a non-vulcanized rubber composition that covers the outer circumference of the anticorrosion coating layer; and a sheet that covers the outer circumference of the elastic body A flexible joint comprising: the elastic body and the sheet having a total thickness of 5 mm or more even at the thinnest portion, and when the original length of the flexible joint is 100. The present invention relates to a flexible joint which can be compressed to a length of 70 or less and can be extended to a length of 130 or more when the original length of the flexible joint is 100.

[0006]

The present inventors have solved the above problems by the following method. The joint body is made of metal that is not easily deformed by earth pressure, etc., and the pipe body is completely sealed by welding or other physical fixing to the front and rear pipe bodies. The flexibility required for the joint body is made bellows-shaped, so that the joint body has strength and flexibility.

Further, a primary anticorrosive coating layer is provided for the purpose of preventing corrosion which is a drawback of the metal joint. Furthermore, in order to prevent the expansion and contraction function from being impaired by clogging with earth and sand in the concave portion formed between the convex portions, which is a drawback when the joint body is made into an uneven bellows shape, the outer periphery of the anticorrosion coating layer is Covered with an elastic body.

The functions required of this elastic body include the following functions in addition to the above. Especially at the time of burying, it prevents damage to the base pipe due to earth and sand and pebbles and propagates the pipes connected to the front and back, vibration of the pump, expansion and contraction of the pipe,
By insulating the vibration from transportation facilities on the ground, the fatigue given to the corrugated joint body is reduced. Further, by providing a waterproof material, water is blocked for a long period of time, and by protecting the joint body having an uneven corrugated shape, which is particularly apt to be corroded under manufacturing conditions, it has a function of enhancing the anticorrosion effect. By the above means, it was confirmed that a composite joint excellent in long-term stability, which was not seen in the past, was obtained, and the present invention was achieved.

[0009]

EXAMPLES The joint body is made of metal such as iron, copper, aluminum, lead, etc., or alloy such as stainless steel, brass, etc. The maximum compression allowance is 70% or less when the original length of the joint body is 100%, and the maximum tensile allowance is 130% or more when the original length of the joint body is 100%. The condition is that the condition of being able to perform tension is satisfied. That is, when the maximum allowable compression amount is 30% or less or when the maximum tensile allowable amount is 30% or less, extremely large displacements such as ground subsidence cannot be followed, and there is a risk of an outflow or jet accident.

The concavo-convex bellows-shaped metal joint body and the pipes connected to the front and rear of the joint body are not particularly limited in terms of materials, but in terms of cost, anticorrosion, and especially in clean water, harmful substances are not eluted. , Iron and stainless steel are preferred. In addition, the inner surface of the joint body is polyethylene, polypropylene, polybutene,
It may be used for anticorrosion and other purposes by lining with other polymer.

Further, in consideration of cost, strength and flexibility, the plate thickness used for the portion of the concavo-convex bellows-shaped metal joint main body should be different from that of the pipes before and after it. Good to have Further, the joint body referred to in the present invention may be any one as long as it can exhibit flexibility by alternately providing irregularities in the longitudinal direction of the pipe, and the concave portion and the convex portion are present on the same circumference of the pipe. Alternatively, the tube may have a spiral shape, and the recess and the projection may be present on the same circumference of the tube.

Next, the anticorrosion coating layer will be described. The anticorrosion coating layer is provided for the purpose of anticorrosion of the joint body, and is made of a material that adheres firmly to the joint body at the time of maximum compression displacement and maximum tensile displacement of the joint body and has an excellent ability to shut off the external environment. Anything will do. Specific examples thereof include those based on thermosetting resins such as epoxy, urethane and unsaturated polyester, and those based on thermoplastic polymers such as polyethylene, polypropylene and polybutene, both of which are used. it can. Further, various adhesion aids can be used together for the purpose of making the adhesion to the joint body stronger and more stable.

Next, the elastic body will be described. Since the joint body has irregularities, especially when it is used for underground burial, the concave part is covered with earth and sand, pebbles, etc., and the expected movement cannot be achieved. Flexibility cannot be exhibited. By covering the outer periphery of the anticorrosion coating layer with the elastic body, the movement originally expected for the joint body can be exhibited. In addition, damage to the joint body due to pebbles or the like can be prevented. Further, by protecting the anticorrosion coating layer, it is possible to exert a stable anticorrosion effect for a longer period of time.

Further, when the joint body is directly buried in the ground, when one of several concave portions and convex portions of the joint body is locally subjected to stress due to ground subsidence, etc. Stress concentrates on. In the present invention, since the outer circumference of the joint body is covered with the elastic body, stress and displacement due to ground subsidence or the like are dispersed in a wide range by the elastic body.

When the elastic body is composed of a reaction product of a main agent containing a liquid rubber and a curing agent, it is necessary to have a hardness of 5 to 60 with an A type hardness meter specified in JIS-K-6301. Also,
This rubber elastic body must have a thickness of 5 mm or more even in the thinnest part. If it is less than 5 mm, it often causes scratches that reach the joint body due to pebbles in the ground, and this portion becomes the starting point of corrosion.

When the elastic body is formed of a non-vulcanized rubber composition, if the non-vulcanized rubber composition is exposed in the ground, creep or compressive strain is likely to occur. Therefore, the outer periphery of the elastic body is covered with the sheet. In this case, the elastic body and the sheet have a total thickness of 5 mm or more even in the thinnest part.

Further, the material of the elastic body is required not to be easily separated from the anticorrosion coating layer, to prevent soil and water from entering the interface between them, and to be hard to be deteriorated even if buried in the soil for a long time. It

As the non-vulcanized rubber composition constituting the elastic body, there is a mixture of non-vulcanized rubber, tackifying resin, filler, plasticizer and the like. Examples of the non-vulcanized rubber include polyisobutylene, recycled butyl rubber, halogenated butyl rubber, butyl rubber, EPT, ethylene propylene rubber, isoprene rubber, BR, SBR, NBR, chloroprene rubber, chlorinated polyethylene, and chlorosulfonated polyethylene.
Acrylic rubber, epichlorohydrin rubber, etc. may be used alone or in combination of two or more. The sheet covering the elastic body can be formed of non-vulcanized rubber, vulcanized rubber, or thermoplastic resin.

Specific examples of the rubber which is liquid at room temperature include silicone, polysulfide rubber, silicone modified urethane, urethane,
The main chain skeleton is butadiene, butadiene-nitrile, butadiene-styrene, hydrogenated butadiene, isoprene, chloroprene, which has a functional group at both ends or has a double bond in the molecule, aniline derivative, polyol, urethane acrylic polyol Etc. can be mentioned. It is necessary to select a curing agent according to these functional groups. Table 1 shows examples of combinations of the functional groups on the liquid rubber side and the functional groups of the curing agent.

[0020]

[Table 1]

Among the above, the hydroxyl group-terminated liquid rubber is excellent in rubber elasticity, water resistance, environmental barrier property and durability of the cured product,
It is possible to easily control the mixability of the main agent and the curing agent and the usable time, and it is excellent in curing reactivity at room temperature, storage stability and economical efficiency. Furthermore, when the main chain skeleton is butadiene or chloroprene, etc., it has excellent compatibility with bituminous substances such as asphalt, and along with it, the environmental barrier ability including water resistance is further improved, and cost reduction is also possible. It is valid.

From the above reasons, among the exemplified liquid rubbers, those not containing an ether bond or an ester bond in the main chain skeleton are preferable in terms of eliminating the cause of hydrolysis. Further, the condition of a liquid rubber having two or more hydroxyl groups in one molecule and a curing agent containing two or more isocyanate groups in one molecule is that a rubber elastic body polymerized by reaction between the liquid rubber and the isocyanate is used. It is a necessary condition to obtain.

Next, examples of commonly used curing agents include epoxy compounds, isocyanate compounds, aziridine compounds, polyamines, peroxides and metal oxides. In the present invention, as described above, an example using an isocyanate compound is particularly preferable. Specific examples thereof include toluylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate,
Isophorone diisocyanate, a prepolymer having a terminal isocyanate group, and block products thereof are used alone or in combination. The curing agent can be used in combination with the plasticizer in consideration of its compounding ratio and viscosity, but in that case, the plasticizer must be dehydrated and not react with isocyanate.

In determining the amount of the curing agent, it is necessary that the reaction molar ratio is 0.6 NCO / OH mol or more and 2.0 NCO / OH mol or less. If it is less than 0.6 NCO / OH mol, it becomes very soft and the hardness condition cannot be satisfied, and the unreacted hydroxyl group becomes too much in the rubber elastic system, resulting in poor water resistance and curing. It is not preferable because it may cause a defect. Conversely, 2.0
If it exceeds NCO / OH mol, the hardness becomes too high, 130% or more of the original length cannot be stretched at the time of pulling, and the cost becomes high, which is not preferable.

The reaction molar ratio (NCO / OH) obtained by dividing the number of moles of isocyanate groups by the number of moles of hydroxyl groups is the hydroxyl group content indicated by the weight percentage of hydroxyl groups in the hydroxyl group-terminated liquid diene rubber and the isocyanate group. It is a value determined by the isocyanate content of the curing agent. This is calculated by the following formula.

Reaction molar ratio (NCO / OH) = {(weight of hydroxyl group-terminated liquid diene rubber × hydroxyl group content) / (weight of isocyanate curing agent × isocyanate group content)} × (molecular weight of NCO) / ( OH molecular weight). Here, (molecular weight of NCO) / (molecular weight of OH) = 42 /
17 = 2.47.

Here, the components constituting the main agent will be briefly described. In the present invention, in achieving a rubber elastic body obtained by reacting a rubber that is liquid at room temperature, if liquid rubber and its curing agent are essential components, only this essential component is possible. . However, in consideration of workability in forming a rubber elastic body, economy, long-term durability after being made into a rubber elastic body, hardness, physical properties against compression and tension, etc., bituminous products and plasticizers are It becomes an essential ingredient. Further, fillers, antioxidants, catalysts, tackifying resins, waxes, pigments, surfactants, coupling agents and the like generally used in the rubber industry, coating industry and the like are used for imparting applications, necessary performances and functions. To
It may be used as appropriate.

In order to more reliably seal the elastic body and the anticorrosion coating layer, a waterproof material made of non-vulcanized rubber viscoelastic body is wound around the outer periphery of the anticorrosion coating layer near both ends of the elastic body. First, it is desirable to form an elastic body.

When the elastic body is composed of a reaction product of a main agent containing liquid rubber and a curing agent, the hardness of the elastic body is JIS-K.
-6301 A type is 5-60. If this is 5 or less,
It is unsuitable because it is too soft and easily damaged, and it is easily pressed by earth and sand and pebbles to hinder the expansion and contraction behavior.
On the other hand, if it is harder than 60, it will not behave unless it is a large stress against compression, and it will be unsuitable because there will be no relaxation for behavior with little displacement such as vibration. It is easy and inappropriate.

When the groove is provided on the outer peripheral surface of the elastic body in the circumferential direction, the elastic body can more easily follow the expansion of the flexible joint. However, if the ratio of the depth of the groove to the distance between the adjacent convex parts of the joint body exceeds 40%, soil, sand,
Pebbles are more likely to be clogged and the groove is blocked. For this reason, the expansion and contraction behavior of the elastic body tends to be obstructed, and the elastic body becomes difficult to function effectively, which is unsuitable.

1, 2, and 3 are sectional views showing a flexible joint according to an embodiment of the present invention. In the example of FIG. 1, the pipe 1A is connected to one end 2a of the metal tubular joint body 2 and the pipe 1B is connected to the other end 2d. The inner peripheral surface and the outer peripheral surface in the joint direction are provided with recesses and protrusions alternately in the longitudinal direction, and the joint body 2 is expandable and contractable in the longitudinal direction. When viewed from the outer peripheral surface side, ring-shaped convex portions 2b and concave portions 2c are provided alternately in the longitudinal direction.

An anticorrosion coating layer 4 is provided so as to cover the outer peripheral surface of the joint body 2. Further, the elastic body 5A covers the outer periphery of the anticorrosion coating layer 4. The outer shape of the elastic body 5A is substantially cylindrical, but the diameter is gradually reduced at the end 5b. The protrusions 5c and the grooves 5d are alternately provided inside the main body 5a. The protrusion 2b is inserted into the groove 5d, and the recess 5c is inserted into the protrusion 5c. Anticorrosion coating layer 4 and elastic body
It is joined to 5A without any gap.

In the example of FIG. 2, four ring-shaped grooves 5e are provided at equal intervals on the outer peripheral surface of the main body 5a of the elastic body 5B. Each groove 5e has a trapezoidal shape with a shallow bottom.
Each groove 5e is provided at the position of each recess 2c. A ring-shaped waterproof material 6A is provided at the interface between the anticorrosion coating layer 4 and the end 5b at the end 2a. At the end 2d, a ring-shaped waterproof material 6B is provided at the interface between the anticorrosion coating layer 4 and the end 5b. The elastic bodies 5A and 5B in FIGS. 1 and 2 are
It consists of a reaction product of a main agent containing liquid rubber and a curing agent.

In the flexible joint shown in FIG. 3, an elastic body is used.
15 consists of a non-vulcanized rubber composition. The main body 15a of the elastic body 15 has a substantially cylindrical outer shape, and both ends of the main body 15a are provided with ends 15b whose diameter gradually decreases toward the ends. Protrusions 15c and grooves 15d are alternately provided inside the main body 15a. The outer surface of the elastic body 15 is covered with the sheet 7.

Next, a method for manufacturing the flexible joint will be described with reference to FIGS. 1 and 3 as an example. FIG. 1: The anticorrosion coating layer 4 is formed on the joint body 2. Next, the mold is assembled, and the space formed between the anticorrosion coating layer 4 and the mold is filled with a mixture of the main agent and the curing agent. Next, a crosslinking reaction is allowed to proceed and the flexible joint is demolded. To prepare the above mixture, liquid rubber, bitumen, a plasticizer and other fillers, an anti-aging agent and the like are mixed, passed through an ink roll twice to form a main component, and mixed with a curing agent.

FIG. 3: Butyl rubber, recycled butyl rubber, polyisobutylene, halogenated butyl rubber, acrylic rubber,
One kind or a combination of epichlorohydrin rubber and the like, for example, a non-vulcanized rubber composition that is kneaded with a tackifier resin, a filler, a plasticizer, etc. by a pressure kneader or the like and adheres and adheres to the anticorrosion coating layer 4 using an extruder or Obtained by molding with a press. Then, the molded rubber obtained by the above method is pressure-bonded onto the anticorrosion coating layer 4 so as not to let air in, and the sheet 7 is placed thereon.
Can be attached to form the elastic body 15. FIG. 4 is a perspective view showing the molded body 15A.

Next, experimental results will be described. (Preparation of Sample) The joint body 2 shown in FIGS. 1 to 3 was manufactured. However, the inner diameter of the joint body 2 was 100 mm, the number of the convex portions 2b was 5, the distance between the vertices of the adjacent convex portions was 30 mm, and the depth of the concave portion 2c was 25 mm. Straight pipes 1A and 1B were welded to both ends of the joint body 2 to have a total length of 310 mm. A polyethylene lining 4 having a thickness of 2 mm was provided on this outer peripheral surface.

A molded body 15A shown in FIG. 4 was produced from a regenerated butyl rubber-based non-vulcanized rubber composition. This molded body 15A was attached onto the above-mentioned joint body 2 while being pressure-bonded so that air bubbles would not enter. A vulcanized butyl rubber sheet 7 with a thickness of 2 mm was attached to the outer periphery of the elastic body 15 to obtain the structure shown in FIG. A comparative example 1 has a thickness (thickness of the thinnest portion) of the elastic body 15 at the apex of the convex portion 2b of 1 mm,
The one having a thickness of 3 mm was used as Example 1 and the one having a thickness of 13 mm was used as Example 2.

Further, a liquid polybutadiene liquid and an isocyanate curing agent were mixed. The above fitting body 1
The mold was attached to, and the above mixture was filled in the cavity in the mold, and this was cured to manufacture the flexible joint shown in FIG. 1 or 2.

The reaction molar ratio between the isocyanate group and the hydroxyl group was changed as shown in Table 2. Of the examples shown in Table 2,
Examples 3, 4 and Comparative Example 2 are the structures shown in FIG.
The thickness of the elastic body 5A (the thickness of the thinnest portion) at the apex of the convex portion 2b was set to 3, 5 or 20 mm. The structures of Examples 5 and 6 and Comparative Examples 3 and 4 are the structures shown in FIG. 2, and the ratio of the depth of the groove 5e to the distance between the vertices of the protrusions 2b is 30% or 50%. Comparative Example 5 is an example in which no elastic body is provided.

The following tests were conducted on the flexible joints of the respective examples. (Compression test) Each specimen was compressed to have a length of 50% of the original length, and the presence or absence of abnormalities such as peeling and rupture of the rubber layer, and the ratio from the original length when abnormalities occurred were obtained. This is shown in Table 2 as "maximum compression deformation amount".

(Tensile Test) Each test piece was pulled so as to be 150% of the original length when the original length was 100%, and the presence or absence of abnormalities such as peeling and breakage of the rubber layer was investigated. . Moreover, the ratio from the original length at the time of occurrence of abnormality was obtained. This is shown in Table 2 as "maximum tensile deformation amount".

(Salt Water Spray Test) For each test piece, a cross cut reaching the stainless steel plate was put in each elastic body, and salt water was sprayed for 1000 hours. Then, the presence or absence of abnormality was visually determined. When an abnormality such as rusting occurred, it was marked with "x", and when there was no abnormality, it was marked with "○".

(Stretching Disorder) The structure of each example was put in a box, and the straight pipes 1A and 1B were taken out of the box. The box was filled with sand and compressed to 50% of its original length. After the test, the flexible joint was taken out from the box. The sand that entered the groove 5e or 3 and interfered with the expansion and contraction was defined as "existence", and the one that was not damaged was defined as "absence".

(Durability Test) The regenerated butyl rubber vulcanized rubber compositions used in Examples 1 and 2 and Comparative Example 1 were molded into a 2 mm thick sheet. Then, a 2 mm thick sheet was prepared from the liquid polybutadiene liquid used in Examples 3 and 4 and Comparative Example 2 and an isocyanate curing agent, and was cured at room temperature for 7 days and at 50 ° C. for 7 days.
I got a cure. Both sheets were punched out into JIS-K-6301 No. 1 dumbbell pieces. Each of them was treated at 80 ° C. × 90% RH for 1 month, 60 ° C. in water for 3 months, 60 ° C. in air for 3 months, or weathered for 1000 hours. After that, tensile stress, elongation and hardness at room temperature were measured at n = 4. Judgment was made based on whether or not the retention rate of the original physical properties was 70% or more, and the retention rate of 70% or more was designated as "○", and the retention rate of less than 70% was designated as "x".

(Flexibility Test for 1000 Times) With respect to the flexible joint of each example, compression to 50% of the original length and extension to 150% of the length were repeated 1000 times. As a result, when there was no abnormality, "○" was displayed.

(Vibration damping effect) The flexible joint of each example was hung at a position 10 mm from both ends, a pickup was attached at a position 30 mm from one end face, and the one end was vibrated. The time until it attenuated to 1/10 of each peak value of the vibration response was measured.

(Noise prevention effect) A flange was attached to one end of the flexible joint of each example. Further, a flange was attached to a part of the rubber powder pneumatic transportation pipe in the factory, and this flange was fixed to the flange of the flexible joint with a bolt. Then, the air transport sound of the rubber powder was measured.

[0049]

[Table 2]

[0050]

[Table 3]

Here, the composition of each elastic body in the above experiment will be shown. First, the composition of the non-vulcanized rubber composition forming the elastic body 15 will be described.

[0052]

[Table 4]

Next, the composition of the vulcanized rubber sheet 7 will be shown.

[0054]

[Table 5]

Next, the composition of the main component containing the liquid rubber is shown below.

[0056]

[Table 6]

As the isocyanate curing agent, "Millionate MTL" manufactured by Nippon Polyurethane Industry Co., Ltd. was used.

As shown in Examples and Comparative Examples, the thinnest portion of the rubber elastic body with respect to the anticorrosion coating layer needs to have a wall thickness of 5 mm or more. As described above, the salt sprayability deteriorates. In other words, this indicates that it is easily damaged by pebbles and the like, and there is a high risk of rusting from the scratched portion. Therefore, if it is 5 mm or more, it is difficult to be scratched, and even if it is scratched, it does not easily rust and can be used for a long time.

Even when the maximum compression deformation amount was 50%, no abnormality occurred in any of the Examples, and an abnormality occurred in Comparative Example 4. In addition, no abnormality occurred in any of the examples even when the maximum tensile deformation amount was 150%. 12 in Comparative Example 4
Abnormality occurred at 0% tension. This has a reaction molar ratio of 2.
This is because it exceeds 0 mol and the hardness is as high as 63, which is outside the range of the present invention. The reaction molar ratio was 0.6 as shown in Examples 5 and 6.
There is no abnormality in the range of NCO / OH mol to 2.0 NCO / OH mol, and the hardness is in the range of 5 to 60. or,
The ratio of the depth of the groove to the length between the vertices of the convex portions was 40% or less, and no expansion / contraction failure occurred.

On the other hand, as shown in Comparative Example 3, 0.6 NCO / O
When the amount is less than H mol, the hardness is too low to be measured and the stretch failure occurs. Also, including the weather, 80 ℃, 90% RH ×
One month, 60 ℃ warm water × 3 months also gave bad results. or,
The expansion / contraction failure is not only caused by the softness, but also the ratio of the groove depth to the length between the convex portions has a great influence, and as shown in Comparative Example 4, the expansion / contraction failure is caused even when the hardness is high.

[0061]

As described above, according to the present invention, a metal flexible joint body having excellent durability is provided with sufficient strength to prevent corrosion and damage of the joint body as a primary anticorrosion coating layer and a sufficient thickness. It was prevented by an elastic body having a to make the corrosion prevention more reliable. Moreover, since the recess of the joint body is sealed by the elastic body, there is a feature that expansion and contraction is not obstructed by earth and sand etc. when buried in the soil, and it has a function as a stable expansion joint for a long period of time, and in case of ground subsidence But it's very safe. Further, since the concavo-convex portion of the joint body is restrained by the elastic body, vibrations from the pump, expansion and contraction of the pipe body, and vibrations from transportation facilities on the ground are also absorbed, which is useful for improving the durability of the flexible joint. In addition, when powder or granules are passed through the pipe, the sound colliding with the flexible joint is significantly reduced, which is also effective in preventing factory noise.

As described above, by using the flexible joint of the present invention in the joint portion of a pipe for transporting gas, liquid, powder, and granules, the safety level at the time of subsidence of the ground is improved, and at the time of burial. There are merits that functions such as ensuring flexibility, ensuring anticorrosion, high vibration damping effect, and noise reduction can be added.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flexible joint according to an embodiment of the present invention, taken along a longitudinal direction.

FIG. 2 is a cross-sectional view of a flexible joint taken along the longitudinal direction.

FIG. 3 is a cross-sectional view of a flexible joint taken along the longitudinal direction.

FIG. 4 is a cutaway perspective view showing a molded body 15A.

[Explanation of symbols]

 1A, 1B Straight pipe 2 Joint body 2a, 2d End part 2b Convex part 2c Concave part 4 Anticorrosion coating layer 5A, 5B Elastic body composed of reaction product of base compound and curing agent 5e Groove 6A, 6B Waterproof material 7 Sheet 15 Unvulcanized Elastic body made of rubber composition

Claims (6)

[Claims] 1. A tubular joint body made of metal, wherein concave portions and convex portions are alternately formed in the longitudinal direction on the inner peripheral surface and the outer peripheral surface of the joint body, and the joint body is deformable in the longitudinal direction. A joint body; an anticorrosion coating layer that covers the outer peripheral surface of the joint body; and an elastic body that covers the outer periphery of the anticorrosion coating layer,
Even the thinnest part has a thickness of 5 mm or more, and consists of a reaction product of a main agent containing liquid rubber and a curing agent. JIS-K-6301
A flexible joint provided with an elastic body having a hardness of 5 or more and 60 or less according to the A-type hardness meter specified in 1., and a length of 70 or less when the original length of the flexible joint is 100. A flexible joint that is compressible up to and can be stretched to a length of 130 or more, given the original length of the flexible joint as 100. 2. A curing agent having a bituminous substance, a liquid rubber having 2 or more hydroxyl groups per molecule and a plasticizer as essential constituents, and a curing agent having 2 or more isocyanate groups per molecule. The reaction molar ratio (NCO /
The flexible joint according to claim 1, wherein OH) is 0.6 or more and 2.0 or less. 3. A groove is provided on an outer peripheral surface of the elastic body in a circumferential direction, and a ratio of a depth of the groove to a distance between adjacent convex portions of the joint body is within 40%. The flexible joint according to 1. 4. A waterproof material made of a non-vulcanized rubber viscoelastic body is provided at an interface between the anticorrosion coating layer and the elastic body in the vicinity of an end portion in the longitudinal direction of the elastic body. Item 1. A flexible joint according to item 1. 5. A tubular joint body made of metal, wherein concave portions and convex portions are alternately formed in a longitudinal direction on an inner peripheral surface and an outer peripheral surface of the joint body, and the joint body is deformable in the longitudinal direction. A joint body; an anticorrosion coating layer that covers the outer peripheral surface of the joint body; an elastic body made of a non-vulcanized rubber composition that covers the outer periphery of the anticorrosion coating layer; and a sheet that covers the outer periphery of the elastic body. A flexible joint, wherein the elastic body and the sheet have a total thickness of 5 mm or more even in the thinnest portion, and the original length of the flexible joint is 10 mm.
A flexible joint that is compressible to a length of 70 or less when 0 and stretched to 130 or more when the original length of the flexible joint is 100. 6. A waterproof material made of a non-vulcanized rubber viscoelastic body is provided at an interface between the anticorrosion coating layer and the elastic body in the vicinity of an end portion in the longitudinal direction of the elastic body. Item 5. The flexible joint according to Item 5.